Interobserver variability - Comparison between liquid-based and conventional preparations in gynecologic cytology

BACKGROUND. Studies have shown that the ThinPrep Papanicolaou test (TP) increases the detection of epithelial cell abnormalities compared with the conventional preparation. Little is known about the interobserver variability of reporting gynecologic cytology results using the TP preparation and its comparison with results obtained using the conventional method. METHODS. To compare the interobserver variability between the TP method and the conventional method for reporting the diagnoses of gynecologic Cytology, 20 pairs of conventional and TP slides (total, 40 slides) that were prepared from split samples were evaluated blindly by 19 cytotechnologists from three different laboratories. Each reviewer was asked to categorize each slide into the following five categories: within normal limits, benign cellular changes, atypical squamous cells of undetermined significance, low-grade squamous intraepithelial lesion (LSIL), and high-grade squamous intraepithelial lesion (HSIL). For both conventional and TP preparations, interobserver variability was analyzed using Spearman rank correlation coefficients. The mean correlation coefficients (weak, 0.0-0.4; fair, 0.4-0.7; and strong, 0.7-1.0) between the TP method and the conventional method were then compared. RESULTS. The overall interobserver agreement as well as interobserver agreement within each laboratory was good for both TP and conventional preparations. Based on the set of conventional cervical smears, only one slide that was diagnosed as HSIL had unanimous agreement; whereas, based on the set of TP slides, three slides, including two diagnosed as HSIL and one diagnosed as LSIL, had a unanimous diagnosis. The difference in the interobserver agreement between TP and conventional methods, based on comparing their mean x standard deviation correlation coefficients (TP method, 0.84 +/- 0.081; conventional method, 0.82 +/- 0.105; P < 0.001), was statistically significant. CONCLUSIONS. Interobserver agreement in reporting gynecologic cytology using the TP method is good, particularly for squamous intraepithelial lesions, and appears to be superior to the conventional method.